Psidium cattleianum is native to Brazil, but has been naturalised in Florida, Hawai'i, tropical Polynesia, Norfolk Island and Mauritius for its edible fruit. It forms thickets and shades out native \nvegetation in tropical forests and woodlands. It has had a devastating effect on native habitats in Mauritius and is considered the worst plant pest in Hawai'i, where it has invaded a variety of natural areas. It benefits from feral pigs (Sus scrofa) which, by feeding on its fruit, serve as a dispersal agent for its seeds. In turn, the guava provides favourable conditions for feral pigs, facilitating further habitat degradation.

Evergreen shrub or small tree up to 8m tall. Mature branches are gray to reddish-brown with peeling bark and young branches are round and pubescent. Leaves are opposite, simple, entire, glabrous, elliptic to oblong, to 8cm (3 in) long. Flowers to 2.5cm (1.2 in) wide, born singly at leaf axils, with white petals and numerous white and yellow stamens. Fruit is a globose berry, 3-6cm (1.2-2.4 in) long, purple-red, with whitish flesh, usually sweet-tasting when ripe; seeds are numerous.

Uses

The strawberry guava is a shrub naturalised in several subtropical areas. It produces sweet and aromatic fruit, which are appreciated by the inhabitants of La Réunion Island. Processing industries are supplied by fruit gathered from the wild. As strawberry guava thrives in humid areas where the farming potential is low, its cultivation could be a means of providing additional income to farmers, while also establishing a steady supply of fruit to industry and to markets (Normand 2002).

Regeneration of strawberry guava is by seed and by root sprouts, which allow it to undergo expansive vegetative reproduction. Strawberry guava produces an abundance of fruits, the seeds of which are dispersed by birds and mammals.Strawberry guava is a prolific fruiter, with up to 70 seeds per fruit, though most fruits contain a lower number of seeds. Fruiting is more abundant for stems on the edge of the thickets.

P. cattleianum is a habitat-altering weed that poses a major threat to endemic flora by competing for light and soil nutrients. Today the most serious threat to Seychelles forests is the low regeneration of native trees caused by the invasion of alien plant species such as P. cattleianum (Fleischmann, 1997, 1999, in Fleischmann et al. 2006).

Management Info

Preventative measures: A Risk Assessment of Psidium cattleianum for Hawai‘i and other Pacific islands was prepared by Dr. Curtis Daehler (UH Botany) with funding from the Kaulunani Urban Forestry Program and US Forest Service. The alien plant screening system is derived from Pheloung et al. (1999) with minor modifications for use in Pacific islands (Daehler et al. 2004). The result is a score of 18 and a recommendation of: \"Likely to cause significant ecological or economic harm in Hawai‘i and on other Pacific Islands as determined by a high WRA score, which is based on published sources describing species biology and behaviour in Hawai‘i and/or other parts of the world.\"

\r\nPhysical: Because of the huge quantities of seed that are dispersed by feral pigs, and other exotic invasive species, feral species management is a practical and necessary first step in strawberry guava management. Manual and mechanical control measures work reasonably well and are recommended where practical. Seedlings and saplings originating from seed can be uprooted. Uprooted plants may resprout or re-root in areas with greater than 2000mm of rain/year or drier areas after prolonged rain, especially if the plants are set on the ground. Manual and mechanical methods are less effective on root sprouts.

\r\nChemical: A number of effective chemical control measures have been developed. Strawberry guava is sensitive to picloram, dicamba, glyphosate, and triclopyr. It has been shown that undiluted picloram (Tordon 22K) is highly effective on strawberry guava as a cut stump treatment. Tordon 22K was used at Hawai‘i Volcanoes but discontinued because of unfavourable effects on non-target plants. It was replaced by Tordon RTU, which was nearly as effective, but less harmful to surrounding vegetation. Undiluted dicamba (Banvel) proved to be highly effective in a cut surface treatment. Additionally, undiluted glyphosate (Roundup) has proven to be effective using a \"\"hack and squirt\"\" method. Resource Managers in Hawai‘i found undiluted triclopyr ester (Garlon 4) to be effective as a cut-stump treatment, with 80% of plants dead and 90% of treated plants without resprouts after 21 months. A frill application of undiluted triclopyr amine (Garlon 3A) was somewhat less effective, with 11 of 20 stems dead and all trees defoliated after 21 months. Fifty percent Garlon 4 and 3A were about 50% effective. A major drawback of cut-stump treatment methods in very wet areas (>5000mm rainfall/yr) was resprouting of slash from cut stump and wood fragments from felling larger trees. Garlon is recommended because of its lack of mobility and relatively short half-life, 4-6 weeks. In addition, the research is more thorough and definitive on control methods for Garlon than other herbicides.

\r\nBiological: Biological control is the only feasible long-term management strategy for strawberry guava. However, until recently, biological control has been perceived as unfeasible because common guava, grown commercially in Hawai‘i, is a congener of strawberry guava. Biological control is being reexamined. Several insects defoliate strawberry guava in its natural range, it is possible that insect biological control agents could be found that do not attack common guava. Memoranda of agreement has been concluded between the University of Hawai‘i and two Brazilian Universities to locate species attacking strawberry guava and not common guava. It is thought that highly specific insect pests can be found because common guava and strawberry guava are sympatric in their natural range.

Informations on Psidium cattleianum has been recorded for the following locations. Click on the name for additional informations.

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Impact information

P. cattleianum is a habitat-altering weed that poses a major threat to endemic flora by competing for light and soil nutrients. Today the most serious threat to Seychelles forests is the low regeneration of native trees caused by the invasion of alien plant species such as P. cattleianum (Fleischmann, 1997, 1999, in Fleischmann et al. 2006).

Preventative measures: A Risk Assessment of Psidium cattleianum for Hawai‘i and other Pacific islands was prepared by Dr. Curtis Daehler (UH Botany) with funding from the Kaulunani Urban Forestry Program and US Forest Service. The alien plant screening system is derived from Pheloung et al. (1999) with minor modifications for use in Pacific islands (Daehler et al. 2004). The result is a score of 18 and a recommendation of: \"Likely to cause significant ecological or economic harm in Hawai‘i and on other Pacific Islands as determined by a high WRA score, which is based on published sources describing species biology and behaviour in Hawai‘i and/or other parts of the world.\"

\r\nPhysical: Because of the huge quantities of seed that are dispersed by feral pigs, and other exotic invasive species, feral species management is a practical and necessary first step in strawberry guava management. Manual and mechanical control measures work reasonably well and are recommended where practical. Seedlings and saplings originating from seed can be uprooted. Uprooted plants may resprout or re-root in areas with greater than 2000mm of rain/year or drier areas after prolonged rain, especially if the plants are set on the ground. Manual and mechanical methods are less effective on root sprouts.

\r\nChemical: A number of effective chemical control measures have been developed. Strawberry guava is sensitive to picloram, dicamba, glyphosate, and triclopyr. It has been shown that undiluted picloram (Tordon 22K) is highly effective on strawberry guava as a cut stump treatment. Tordon 22K was used at Hawai‘i Volcanoes but discontinued because of unfavourable effects on non-target plants. It was replaced by Tordon RTU, which was nearly as effective, but less harmful to surrounding vegetation. Undiluted dicamba (Banvel) proved to be highly effective in a cut surface treatment. Additionally, undiluted glyphosate (Roundup) has proven to be effective using a \"\"hack and squirt\"\" method. Resource Managers in Hawai‘i found undiluted triclopyr ester (Garlon 4) to be effective as a cut-stump treatment, with 80% of plants dead and 90% of treated plants without resprouts after 21 months. A frill application of undiluted triclopyr amine (Garlon 3A) was somewhat less effective, with 11 of 20 stems dead and all trees defoliated after 21 months. Fifty percent Garlon 4 and 3A were about 50% effective. A major drawback of cut-stump treatment methods in very wet areas (>5000mm rainfall/yr) was resprouting of slash from cut stump and wood fragments from felling larger trees. Garlon is recommended because of its lack of mobility and relatively short half-life, 4-6 weeks. In addition, the research is more thorough and definitive on control methods for Garlon than other herbicides.

\r\nBiological: Biological control is the only feasible long-term management strategy for strawberry guava. However, until recently, biological control has been perceived as unfeasible because common guava, grown commercially in Hawai‘i, is a congener of strawberry guava. Biological control is being reexamined. Several insects defoliate strawberry guava in its natural range, it is possible that insect biological control agents could be found that do not attack common guava. Memoranda of agreement has been concluded between the University of Hawai‘i and two Brazilian Universities to locate species attacking strawberry guava and not common guava. It is thought that highly specific insect pests can be found because common guava and strawberry guava are sympatric in their natural range.

Daehler, C.C; Denslow, J.S; Ansari, S and Huang-Chi, K., 2004. A Risk-Assessment System for Screening Out Invasive Pest Plants from Hawaii and Other Pacific Islands. Conservation Biology Volume 18 Issue 2 Page 360.Summary: A study on the use of a screening system to assess proposed plant introductions to Hawaii or other Pacific Islands and to identify high-risk species used in horticulture and forestry which would greatly reduce future pest-plant problems and allow entry of most nonpests.

IUCN/SSC Invasive Species Specialist Group (ISSG)., 2010. A Compilation of Information Sources for Conservation Managers.Summary: This compilation of information sources can be sorted on keywords for example: Baits & Lures, Non Target Species, Eradication, Monitoring, Risk Assessment, Weeds, Herbicides etc. This compilation is at present in Excel format, this will be web-enabled as a searchable database shortly. This version of the database has been developed by the IUCN SSC ISSG as part of an Overseas Territories Environmental Programme funded project XOT603 in partnership with the Cayman Islands Government - Department of Environment. The compilation is a work under progress, the ISSG will manage, maintain and enhance the database with current and newly published information, reports, journal articles etc.

Kueffer, C. and Mauremootoo, J., 2004. Case Studies on the Status of Invasive Woody Plant Species in the Western Indian Ocean. 3. Mauritius (Islands of Mauritius and Rodrigues). Forest Health & Biosecurity Working Papers FBS/4-3E. Forestry Department, Food and Agriculture Organization of the United Nations, Rome, Italy.

Mauremootoo, J. R. unpublished. CBD case study - guava in Mauritius.Summary: This article reviews the status of Psidium in Mauritius, its impact on native biodiversity, the efforts being made to control the species and possible future avenues for management.

Stone, C. P., Smith, C. W. and Tunison, J. T. 1992. Alien Plant Invasions in Native Ecosystems of Hawaii. Management and Research. University of Hawaii Cooperative Park Studies Unit: 1-887.Summary: This large and comprehensive volume covers general features of invasive species biology, case studies of invasive species management in the US, the pest status & autecology of some of the major invasives in Hawaii, methods used for the control.

Strahm, W. A. 1999. Invasive species in Mauritius: examining the past and charting the future. In Invasive Species and Biodiversity Management. Kluwer Academic Publishers: 325-347.Summary: This article reviews the history of introduced animals and plant in Mauritius and their effects on the indigenous flora & fauna. Management measures are reviewed & illustrated with case studies. Future prospects for invasive species management are discuss

Lorence, D. and Sussman, R. W. 1986. Exotic species invasion into Mauritius wet forest remnants. Journal of Tropical Ecology 2: 147-162.Summary: Two areas of wet forest were sampled to determine the extent of invasion by weed species. In both cases the canopy was dominated by native species but the seedling layer by introduced species, notably Psidium and Ligustrum.

Morton, J. F. 1987. Fruits of Warm Climates.Summary:Psidium cattleianum is cultivated to a limited extent in other areas of South America and Central America and in the West Indies, Bermuda, the Bahamas, southern and central Florida and southern California. It is grown occasionally in subtropical Africa

Geographic region: Pacific, Indian OceanEcosystem: Terrestrial Expert in the botany of French Polynesia and the Pacific Islands, and has worked on ecology and biological control of Miconia calvescens in French Polynesia.